A curable composition has been variously improved depending on the application, and widely used as a material for optical components or molded products, an adhesive, a coating agent, and the like. For example, a curable composition that produces a cured product having excellent transparency is normally used as a material for optical components or a coating agent, and a curable composition that produces a cured product having high adhesion is normally used as an adhesive or a coating agent.
In recent years, a curable composition has also been used as an optical device-securing composition (e.g., optical device-securing adhesive or optical device sealing material) when producing a sealed optical device.
Examples of the optical device include various kinds of lasers (e.g., semiconductor laser diode (LD)), a light-emitting device (e.g., light-emitting diode (LED)), a light-receiving device, a hybrid optical device, an optical integrated circuit, and the like. In recent years, an optical device that emits blue light or white light having a short peak wavelength has been developed, and widely used. The amount of heat generated by optical devices tends to increase due to a significant increase in brightness of light-emitting devices with a short emission peak wavelength.
Along with an increase in brightness of optical devices, a cured product of an optical device-securing composition may deteriorate when exposed to light having higher energy or a higher temperature generated by an optical device, so that cracking or delamination may occur.
In order to solve this problem, Patent Documents 1 to 3 propose an optical device-securing composition that contains a polysilsesquioxane compound as the main component.
However, a cured product of each optical device-securing composition disclosed in Patent Documents 1 to 3 may not exhibit sufficient heat resistance and transparency while exhibiting sufficient adhesion.
As an optical device sealing composition, Patent Document 4 proposes an epoxy resin composition that contains an alicyclic epoxy resin, and Patent Document 5 proposes an epoxy resin composition that contains a polythiol compound.
However, these compositions may not exhibit sufficient light resistance over time, or may show a decrease in adhesion.